"Nevin was a wonderful player but also a wonderful person. He was well liked by everyone who knew him and his loss will be deeply felt by his team-mates and everyone at Ulster Rugby.

"He will be sorely missed and the thoughts of everyone involved in the game are with his family at this time."

Irish Rugby Football Union president Billy Glynn also expressed his condolences.

A statement from Glynn released by the IRFU read: "This is a terrible tragedy that has struck the Spence family and the thoughts of everybody in Irish Rugby are with them at this time.

"Nevin was an outstanding young player which was evident from his progression through the representative ranks and the game has been robbed of a very talented young man.

"On behalf of Irish Rugby, I would like to offer our heartfelt support to the family, friends and team-mates of Nevin during this difficult time."

The Northern Ireland Ambulance Service (NIAS) said it responded to a 999 call at about 6.15pm following reports that at least three people had fallen into a slurry tank.

The Northern Ireland Fire and Rescue Service also attended and rescued four people from the slurry pit.

Following the lengthy rescue operation it was confirmed that three men had died and a woman was taken to hospital for treatment for the inhalation of fumes.

A spokesman for the ambulance service said: "Three were unconscious and NIAS paramedics commenced resuscitation efforts immediately assisted by other ambulance personnel.

"One of the four showed initial signs of responding to the efforts of the crews and was transported immediately to the nearby Lagan Valley Hospital, where unfortunately he died a short time later.

"Despite the best efforts of all involved the other two men died at the scene.

"A female was treated at the scene and taken to the Royal Victoria Hospital where she is recovering from the effects of fume inhalation."

Ulster fly-half Ian Humphreys led the tributes on Twitter to his former team-mate, who was a member of the squad that reached the Heineken Cup final last season and was predicted to have a glittering international career ahead of him.

Spence made 42 senior appearances for Ulster and was named Young Player of the Year at last year's Irish Rugby Football Union Players' Association Awards. He played for the UlsterRavens, the club's 'A' team, against Munster A on Friday.

Humphreys wrote: "Devastated to hear the news about Nevin Spence and his brother and dad. Prayers with all his family... RIP Nev, you'll never be forgotten..."

Northern Ireland First Minister Peter Robinson wrote: "Deeply saddened to hear of the tragedy in Hillsborough this evening. My thoughts and prayers are with family at this time of devastation."

Tributes also appeared on feeds representing both the British and Irish Lions and the RaboDirect Pro12, the league in which Ulster play.

The Lions post read: "All our thoughts are with the family and friends of Ulster centre Nevin Spence, his father and brother."

The post on the Pro12 account read: "Shocked. We just read about Nevin Spence. RIP. There are no words."

Former Ireland and Munster hooker Jerry Flannery added: "Terrible news on Nevin Spence, his Brother and their Dad. Offering up prayers for their family and friends, unbelievably sad."

Former Wales winger Shane Williams wrote: "My thoughts and prayers go out to the family of Nevin Spence. A tragic loss. A class act on the field also. RIP."

Tributes also came from notable Northern Irish sportsmen Rory McIlroy and Barry McGuigan.

McIlroy, golf's world number one, wrote on his Twitter account: "Just heard the tragic news of Nevin Spence and his family. Makes you cherish every day you have on this Earth."

Former boxer McGuigan wrote: "Tragic news about Nevin Spence and his family, in County Down Northern Ireland. My deepest heart felt sympathy to his family."